C4 photosynthesis under optimal conditions confers a higher efficiency ofenables higher-efficiency use of light, water, and nitrogen use than the C3 form used by many of our crops. It is associated with the most productive terrestrial plants and crops. But, it is largely limited to the tropics and subtropics. It has been argued that the high productivity associated with C4 photosynthesis is inherently limited to warm environments or warm temporal/spatial niches in colder climates. A small group of C4 species appear to have overcome this, and in contrast to our the major current C4 crops, maize, sorghum and sugarcane, these species are able to acclimate their photosynthetic apparatus to chilling conditions. This will be illustrated by comparing the responses of cold tolerant Miscanthus x giganteus and Spartina pectinata to cold-intolerant maize. The mechanisms underlying this difference and the potential of introducing these changes into maize and other warm-climate C4 crops will be reviewed.